The securing of data during transmission has been of interest throughout human history. Secure communication has been an essential part of commerce since time immemorial.
More recently, and especially since the widespread availability of computing power and technical means of data transmission, with sophisticated means of securing data transmitted over telecommunications channels and equally sophisticated technical means of decrypting messages, there has developed a rapidly-accelerating race between those who wish to secure messages and those who wish to “crack” them.
There is a constant search for new technical means of securing data during transmission by increasing the threshold of feasibility of decryption, and an equally constant search for means of rendering feasible decryptions that were thought to be infeasible. Similarly, the processing and transmission costs of sending information securely are of concern. The volume of data to be transmitted in the course of business transactions is increasing, and the cost of using public networks is constantly decreasing, while the cost of using private networks is ever more costly. It would be advantageous to be able to send more data, especially in bulk data applications, over less costly open channels, such as the Internet, but it is difficult to secure transmissions over such a medium to the standard normally required for commercial confidentiality purposes.
There have been attempts to alleviate the problem of combining security with low cost.
Published European patent application number EP 0 993 142 A1, for example, proposes a method for providing security for data wherein the bulk of transmitted data is encrypted and transmitted over an inherently less secure channel while selected segments of data are transmitted over a normally private channel, such as the telephone network. An eavesdropper on the less secure channel is thus prevented from reading all the data. Disclosed also is the notion of using one or more scrambling algorithms to scramble data according to a formula derived from the data itself.
Published PCT patent application number WO 00/18078 proposes a method whereby a message is split and transmitted over two channels in such a manner that the portion of the message to be sent over the less secure channel is encrypted, while the portion transmitted over the secure channel remains unencrypted.
It is desirable to find a way of further increasing the security of a message by reducing the computational feasibility of an unauthorized person's recovering the information content of the message and reducing the cost of processing and transmission.